In the prior art there are known several constructions of centrifugal-piston or rotary-piston engines (herein further called ORPE), which are intended to eliminate certain disadvantages of conventional piston engines. E.g., such constructions are described in DE3907307, U.S. Pat. No. 6,279,518, U.S. Pat. No. 4,334,506, WO2005098202, RU2143572, and JP7113452. The latter, for instance, has the purpose “to suppress the side pressure applied to a piston, improve efficiency, reduce vibration and drastically reduce dimension and weight, by revolving a cam on the inner wall of an ellipse without using a crank, in reciprocating motion.” The other above indicated constructions typically have similar purposes.
DE3907307 discloses a four-stroke engine wherein a cylinder block revolves inside a rotor, which is complicated, has a small resource of the valve system, and a des-balance with the revolving system including movable parts.
U.S. Pat. No. 6,279,518 discloses a four-stroke engine having a valve system and a conically shaped rotor. FIG. 7 shows a conical rotor with an elliptical groove, and a series of pistons followers inside the groove. It is a complicated unit with substantial friction losses, which has a limited operation resource for its loaded parts. The construction does not eliminate the side forces exerted by the piston upon the cylinder walls.
RU 2143572 discloses a four-stroke engine, wherein the cylinder block revolves at an elliptical trajectory, and the inlet/outlet system includes a rotatable valve. The construction is complicated and difficult to balance (which is admitted by its author). The piston acts via its rod and a sliding bearing upon an elliptical housing. The place of contact with the housing experiences high friction and heating, and thus will have a short operation resource.
From the instant inventors' point of view, a more advanced design of OPRE is presented in U.S. Pat. No. 6,161,508. It describes “a radial-piston engine of rotary type of the kind having a valve system comprising apertured disc rings arranged in intersliding relationship, one of said rings being stationary while the other one is arranged to take part in the rotary motion of the rotor. The valve opening relationship is determined by the manual angular positions of the discs. In accordance with the invention, filed injection takes place via an injection nozzle positioned in the stationary disc. The valve ring is formed with a through opening which in response to the position assumed my the rotor at the moment of fuel ignition forms an open communication means between the injection nozzle and the combustion chamber.”
That engine however has also certain drawbacks and limitations. It is built as a four-stroke engine having a cylinder block revolving around and impelling a rotor. Reaction forces produced in support bearings are very significant that leads to a short operation resource period. It uses an inlet/outlet system based on a rotatable sliding valve. This necessitates the use of complicated sealing means that, as a rule, have very limited operation resource (typically 100 hours maximum). The rotating cylinder block with linearly reciprocating pistons is very hard to balance, and thusly will cause intensive destructive vibrations. These problems are successfully resolved in the present invention.
A reciprocating rotary engine is taught in U.S. Pat. No. 4,334,506: “Rotary engine having a hollow, stationary block with manifolds for air inlet and exhaust valving and means for supplying fuel. The block supports one or more in-line cylinders which are provided with opposed pistons equipped with rigid and constrained piston rods. The rods carry bearings that run along a cam track surface interior to a disc, the outer surface of which is a right circular cylinder. The surrounding right circular cylinder rotates as a result of the linear movement of the opposed pistons thereby providing mechanical power. The cam surface is a continuous track which determines the out-put motion of the piston movement between top and bottom dead center. Arcuate areas at top and/or bottom dead center permit constant volume combustion and/or exhaust as desired during a particular cycle, whether that cycle be Otto or Diesel and whether it be two or four stroke.” At least one of drawbacks of that design is that the spark plugs 48 and fuel lines 46 are situated inside the rotor. Hence, their replacement would require dissembling the entire engine, which makes maintenance of the engine taught in U.S. Pat. No. 4,334,506 more difficult.
Another example of ORPE, described in U.S. patent application Ser. No. 11/827,595 filed on Jul. 12, 2007 by the instant applicants, employs a non-typical form of conversion of the spinning motion of a rotor into a progressive linear stroke of a piston, and vice versa. This constructive solution provides for substantial absorption of side forces exerted by the piston onto the engine cylinder's walls and vice-versa, and for an essential improvement of the weight and fuel consumption/power output ratios, demonstrating useful advantages over all presently utilized engines known to the applicants, including the Wankel rotor engine.
U.S. patent application Ser. No. 11/827,595, hereby entirely incorporated by reference, discloses a two-stroke opposite rotary-piston engine that comprises a cylinder block including a sleeve and two pistons slidely disposed therein and oppositely movable, which pistons are forming a common combustion chamber situated between their heads, and forming a first gap with sleeve's sidewalls; a rotor having a surface formed by a closed symmetrical Cassini line (particularly, ellipse); traverses attached to the pistons; rollers attached to the traverses and springly depressed against the rotor; oil tubes with end bushings; oil supply and withdraw means; two plungers disposed in each tube forming a second gap with the tube's sidewalls, essentially less than the first gap. The plungers are attached to the traverses and oppositely movable, also including through throttling channels, outward surfaces forming external spaces with the bushings, and inward surfaces forming an internal space with the tube sidewalls, which internal space communicates with the oil supply means and the oil withdraw means. Engine's oil drain means communicate the external spaces with the oil supply means. The engine absorbs side and inertial forces, is more efficient and clean.
However, the design of engine taught in U.S. patent application Ser. No. 11/827,595 has certain drawbacks: the rotor has a significant size and weight, the support roll bearings don't allow absorbing high loads, which shortens the service lifespan thereof. The power takeoff is carried out upon each 180-degree turn, i.e. the load characteristic is uneven that also reduces the lifespan and efficiency of that engine.
The design ideas are further developed in the parent application that proposes a two-stroke opposite radial rotary-piston engine, “comprising a block including sleeves, pairs of pistons disposed within the sleeves and oppositely movable, guiding bearings, a power takeoff shaft, rotors mounted thereon having an inner surface formed by a closed curved line, the rotors' transverse axes are predeterminedly disposed. On the frontal part, the rotors have concaved surface portions along the curved line. T-like traverses are mounted, pair-wise spanning the pistons. The traverses include convex protrusions, cooperating with the concaved portions during the start of the engine. A clearance between the concaved and convex portions is provided after the start. The engine comprises support bearings, coupled to traverses. Support bearings include an external bushing, rolling over the inner surface of the rotor associated with the traverse, thereby impelling the rotor.”
Further analysis of the engine presented in the parent application (particularly its module embodiment EM shown on FIGS. 4a and 5a thereof) has revealed the following design shortcomings: (a) the support bearings experience relatively high load that diminishes their service life; (b) the traverse's protrusion A (FIG. 1b of the parent application) is designed to provide strike-less start of the engine, while clearance between the concaved surface M of the rotor and the convex protrusion A is provided after the start; however when the start is provided by a starter, the rotor can be engaged with the protrusion A in a strike-like manner that may cause breakage of one of these elements; (c) a bending force moment MB=R2×a, causes a higher wear of the friction pair of the piston and the slipper bearing that also shortens their service life.